Patients suffering from respiratory disease (e.g., cystic fibrosis) often display debilitating obstruction of the small airways. The complex architecture of the lungs has hampered efforts to characterize function in this region of the lungs. The long-term goal of the principal investigator is to develop systems for studying small airway function and subsequently characterize the defense mechanism in this region of the lungs. One objective of this project is to improve techniques for isolating and culturing small airway epithelial cells, making the preparations suitable for in vitro studies of small airway epithelial function. Monoclonal antibodies to cell surface antigens will be produced and used to purify cells by fluorescence activated cell sorting and cell- affinity chromatography. The yield and functional quality of cultures will improved by developing serum-free hormone- supplemented media. These techniques will subsequently be used to study salt and water balance across sheets of rabbit, dog, and human small airway epithelial cells in culture. Transepithelial ion fluxes will be measured using radioisotopes, electrochemical driving forces will be determined using microelectrodes, and mechanism which control ion transport processes will be investigated.